In vehicles with an active hydraulic tilting of the car body, the tilting is usually controlled by two servo functions, one per bogie, each function comprising a servo valve, hydraulic cylinder(s) and some form of mechanical bolster. Such multi-function systems involve the risk that the two (or the different) servo functions may start acting against each other via the relatively torsionally rigid car body, which gives diagonal unloading and loading stresses on the wheels of the two bogies. This, in turn, may entail a risk of derailment and this eventuality thus requires an extensive monitoring system. (See further FIG. 1 and the associated text.)
From, for example, Swedish patent specification 381 012, a similar arrangement is already known, in which the distance between the car body and the different bogies on both sides of the car body is measured for the purpose of obtaining an output quantity, which constitutes a measure of the rotation of the different bogies in relation to the car body. The intention is to obtain a fast indication of the vehicle's entry into and exit out of a track curve. This signal together with, for example, the lateral acceleration signal, may be utilized as control signal(s) to the tilting system of the vehicle. The intention is to develop a tilting system which provides a comfortable journey for the passengers without any significant influence of lateral acceleration, and to make possible greater train speeds. It is also desired to avoid sensitivity to any unevenness of the track.